Magnetic disk apparatus

ABSTRACT

Disclosed is a magnetic disk apparatus which protects magnetic disks against external and internal magnetic fields and electromagnetic waves. This magnetic disk apparatus comprises at least one magnetic disk; rotation unit for rotating the magnetic disk; a magnetic head for recording and reproducing information on and from the magnetic disk; an actuator for supporting the magnetic head and moving the magnetic head to a given position on the magnetic disk; and an enclosure for covering those individual components. According to one aspect of this invention, the enclosure is made of a ferromagnetic material. According to another aspect of this invention, the enclosure is made of a non-magnetic material and a shield layer made of a ferromagnetic material is provided at least in that region of an inner wall of the enclosure which corresponds to the movable range of the magnetic head. According to a further aspect of this invention, this apparatus further comprises a circuit board provided on the inner wall of the enclosure, circuitry for accomplishing magnetic recording and reproduction being mounted on the circuit board, and a shield layer provided between the enclosure and the circuit board. According to a still further aspect of this invention, this apparatus further comprises a circuit board provided on the inner wall of the enclosure, circuitry for accomplishing magnetic recording and reproduction being mounted on the circuit board, and a conductive shield member provided between the magnetic disk and the circuit board.

RELATED APPLICATION

This is a continuation of application Ser. No. 08/128,488, filed on Sep.28, 1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic disk apparatus havingmagnetic disks and magnetic heads provided within its enclosure, and,more particularly, to a magnetic disk apparatus which protects themagnetic disks and magnetic heads from an external electromagneticfield.

2. Description of the Related Art

A magnetic disk apparatus has rotatable magnetic disks and magneticheads for writing and reading information on and from the magneticdisks. Each magnetic head is positioned over a desired track position ofthe associated magnetic disk to read data from that track or write datathereon.

This magnetic disk apparatus is widely used as an external storagedevice. To meet the recent demand of downsizing of computer systems,particularly, the use of such a magnetic disk apparatus in a notebooktype computer, a word processor, a portable, palmtop computer and soforth becomes popular. There is therefore a demand for small and slimmagnetic disk apparatuses, such as a 1.8-inch magnetic disk apparatus.As micro magnetic disk apparatuses with a size of 1.8 inches or lesshave the size of a credit card, this type of magnetic disk apparatus canbe detachably mounted in a computer and can be handled alone.

When this magnetic disk apparatus is handled alone unlike the oneinstalled in a computer, it is susceptible to an external magnetic fieldand external electric noise, thus causing a read/write error. If thedetachable magnetic disk apparatus is dropped on a floor or the like byaccident, it would receive a great shock, which may damage the internalcomponents.

This magnetic disk apparatus therefore requires good shock resistance,resistance to the external magnetic field and electric noise resistance.As means to reduce an external shock on the magnetic disk apparatus, ithas been proposed to provide a shock absorber near the magnetic heads toprevent the head from being damaged by a shock (see Japanese UnexaminedPatent Publication No. 168985/1991).

To protect magnetic disks from the internal magnetic field generated bythe actuator in the magnetic disk apparatus, there has been proposed ashield structure such that the base on which the actuator is mountedshould be made of a ferromagnetic material (see Japanese UnexaminedPatent Publication No. 63077/1984).

While the shield structure of the conventional magnetic disk apparatuscan shield an internal magnetic field, however, it cannot shield anexternal magnetic field. Accordingly, the read/write characteristic ofthe magnetic heads is impaired by the external magnetic field. In thevertical magnetic recording system, data on some magnetic disks may beerased by the external magnetic field. As a solution to those problems,the entire magnetic disk apparatus may be shielded by a metal plate orthe like. This measure however causes the size of the apparatus toexceed the form factor size of the apparatus, increasing the space theapparatus needs for its installment. Further, since no measures havebeen taken against external electromagnetic noise as well as internalelectromagnetic noise, those noises are likely to cause a data error.

Furthermore, in a contact type magnetic recording system, wear-outpowder is produced by the contact, thus reducing the contact typemagnetic recording performance.

SUMMARY OF THE INVENTION

It is therefore a primary object of the present invention to provide amagnetic disk apparatus designed to reduce the influence of an externalmagnetic field on the magnetic recording/reproducing characteristicwithout altering the size of the apparatus.

It is another object of this invention to provide a magnetic diskapparatus designed to reduce the influence of external electromagneticwaves on the magnetic recording/reproducing characteristic withoutaltering the size of the apparatus.

It is a further object of this invention to provide a magnetic diskapparatus designed to reduce the influence of internal electromagneticwaves on the magnetic recording/reproducing characteristic withoutaltering the size of the apparatus.

It is a still further object of this invention to provide a magneticdisk apparatus which improves the performance of the contact typemagnetic recording system.

To achieve the foregoing and other objects and in accordance with thepurpose of the present invention, according to one aspect of thisinvention, there is provided a magnetic disk apparatus which comprisesat least one magnetic disk; rotation means for rotating the magneticdisk; a magnetic head for recording and reproducing information on andfrom the magnetic disk; an actuator for supporting the magnetic head andmoving the magnetic head to a given position on the magnetic disk; andan enclosure, made of a ferromagnetic material, for covering thoseindividual components.

As the ferromagnetic material has a function to shield a magnetic field,this structure can prevent the characteristic of the magnetic head frombeing reduced by an external magnetic field and can prevent data on amagnetic disk from being erased by an external magnetic field. Further,as the enclosure itself has this external-magnetic-field shieldingfunction, the shielding of the external magnetic field can beaccomplished without changing the size of the magnetic disk apparatus.

According to another aspect, a magnetic disk apparatus comprises atleast one magnetic disk; rotation means for rotating the magnetic disk;a magnetic head for recording and reproducing information on and fromthe magnetic disk; an actuator for supporting the magnetic head andmoving the magnetic head to a given position on the magnetic disk; anenclosure, made of a non-magnetic material, for covering thoseindividual components; and a shield layer made of a ferromagneticmaterial and provided at least in that region of an inner wall of theenclosure which corresponds to a movable range of the magnetic head.

As the ferromagnetic material has a function to shield a magnetic field,this structure can prevent the characteristic of the magnetic head frombeing reduced by an external magnetic field. Further, as the enclosurecan be made of a light non-magnetic material, the magnetic diskapparatus can be made lighter while accomplishing the shielding of theexternal magnetic field.

According to a further aspect of this invention, a magnetic diskapparatus comprises at least one magnetic disk; rotation means forrotating the magnetic disk; a magnetic head for recording andreproducing information on and from the magnetic disk; an actuator forsupporting the magnetic head and moving the magnetic head to a givenposition on the magnetic disk; an enclosure for covering thoseindividual components; a circuit board provided on an inner wall of theenclosure, circuitry for accomplishing magnetic recording andreproduction being mounted on the circuit board; and a shield layerprovided between the enclosure and the circuit board.

With this structure, the shield layer can shield electromagnetic waves.By providing a circuit-mounted board in the enclosure, therefore, evenwhen the size of the apparatus including the circuit board is set withina predetermined form factor, the circuit will not malfunction due to anexternal electromagnetic wave. What is more, this can be accomplishedwithout altering the size of the magnetic disk apparatus.

According to a still further aspect of this invention, a magnetic diskapparatus comprises at least one magnetic disk; rotation means forrotating the magnetic disk; a magnetic head for recording andreproducing information on and from the magnetic disk; an actuator forsupporting the magnetic head and moving the magnetic head to a givenposition on the magnetic disk; an enclosure for covering thoseindividual components; a circuit board provided on an inner wall of theenclosure, circuitry for accomplishing magnetic recording andreproduction being mounted on the circuit board; and a conductive shieldmember provided between the magnetic disk and the circuit board.

With this structure, the conductive member has a function to shieldelectromagnetic waves. By providing a circuit-mounted board in theenclosure, therefore, even when the size of the apparatus including thecircuit board is set within a predetermined form factor,. thecharacteristic of the magnetic head will not be affected by anelectromagnetic wave generated by the circuit. What is more, this can beaccomplished without altering the size of the magnetic disk apparatus.

According to a yet still further aspect of this invention, a magneticdisk apparatus comprises at least one magnetic disk; rotation means forrotating the magnetic disk; a magnetic head for recording andreproducing information on and from the magnetic disk while in contactwith the magnetic disk; an actuator for supporting the magnetic head andmoving the magnetic head to a given position on the magnetic disk; anenclosure for covering those individual components; and a dust shieldmember for removing dust off a surface of the magnetic disk.

With this structure, even in a contact type magnetic recording system,it is possible to prevent the performance of the contact type magneticrecording from being reduced by dust produced by the contact typemagnetic recording.

Other features and advantages of the present invention will becomereadily apparent from the following description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a perspective view of a magnetic disk apparatus according toone embodiment of the present invention, showing the interior.

FIG. 2 is a perspective view showing the base side of the magnetic diskapparatus in FIG. 1;

FIG. 3 is a cross-sectional view of the magnetic disk apparatus in FIG.1;

FIG. 4 is an enlarged view of the essential portions of the magneticdisk apparatus in FIG. 3;

FIG. 5 is an exploded perspective view of a magnetic head assembly shownin FIG. 1;

FIG. 6A is a perspective view of a magnetic head chip shown in FIG. 5;

FIG. 6B is a cross-sectional view of the magnetic head chip shown inFIG. 5;

FIG. 7 is an exploded perspective view of a flexible support shown inFIG. 5;

FIG. 8 is a cross-sectional view of the magnetic head assembly shown inFIG. 5;

FIG. 9 is an exploded perspective view of the magnetic disk apparatusshown in FIG. 1;

FIG. 10 is a diagram for explaining a printed circuit board of themagnetic disk apparatus;

FIG. 11 is a top view of the magnetic disk apparatus with the topremoved;

FIG. 12 is a cross-sectional view showing the essential portions of themagnetic disk apparatus;

FIG. 13 is a diagram for explaining where shock absorbers of themagnetic disk apparatus are arranged;

FIG. 14 is a diagram for explaining where a ferromagnetic member of themagnetic disk apparatus is arranged;

FIG. 15 is a cross-sectional view showing the essential portions of amodification of the magnetic disk apparatus of this invention;

FIG. 16 is a cross-sectional view showing the essential portions ofanother modification of the magnetic disk apparatus of this invention;

FIG. 17 is a cross-sectional view showing the essential portions of afurther modification of the magnetic disk apparatus of this invention;

FIG. 18A is a diagram showing the exterior of a still anothermodification of the magnetic disk apparatus of this invention;

FIG. 18B is a cross-sectional view Of the magnetic disk apparatus inFIG. 18A;

FIG. 19A is a diagram showing the exterior of a still furthermodification of the magnetic disk apparatus of this invention;

FIG. 19B is a cross-sectional view of the magnetic disk apparatus inFIG. 19A;

FIG. 20 is a perspective view showing the essential portions of a yetstill further modification of the magnetic disk apparatus of thisinvention; and

FIG. 21 is a cross-sectional view showing the essential portions of themagnetic disk apparatus in FIG. 20;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a perspective view of a magnetic disk apparatus according toone embodiment of the present invention, showing the interior, FIG. 2 isa perspective view showing the base side of the magnetic disk apparatusin FIG. 1, FIG. 3 is a cross-sectional view of the magnetic diskapparatus in FIG. 1, and FIG. 4 is an enlarged view of the essentialportions of the magnetic disk apparatus in FIG. 3.

As shown in FIGS. 1 and 2, a base 11 constitutes a bottom plate of adisk enclosure (hereinafter called "housing") of a magnetic diskapparatus. The base 11 is made of a ferromagnetic material, such as ironor Permalloy, to shield an external magnetic field. A flexible printedboard (circuit board) 15a is provided on the bottom of the base 11,except for where a spindle motor 2 and an actuator 3 both to bedescribed later are provided. Mounted on this printed circuit board 15ais an LSI (circuitry for magnetic recording and reproduction) 16.

A plurality of shock absorbers 54, which will be described later, areprovided on this printed circuit board 15a in the vicinity of theperiphery of magnetic disks 28, as shown in FIG. 2. Further, a shieldmember 51 made of a metal plate, such as a copper plate, having a goodconductivity, is provided on the shock absorbers 54 for accomplishingelectric shield. A ferromagnetic member 53 is provided in associationwith the location of magnetic heads 4 to provide magnetic shield for themagnetic heads 4.

Provided on the right side of the base 11 are a magnetic circuit 14 andthe actuator 3. Attached to this actuator 3 are arms 34 to which contacttype magnetic heads (assembly) 4 are provided. The magnetic heads 4 willbe described later with reference to FIGS. 5 through 8. Attached to theside of the actuator 3 is a flexible cable 36 provided with a head ICthat is connected to the magnetic heads 4 by lead wires. The other endof the flexible cable 36 is securely and electrically connected to theprinted circuit board 15a.

Provided in the center of the base 11 is the spindle motor 2 thatrotates the magnetic disks 28. The magnetic disks 28, 1.8 inches indiameter, are attached to this spindle motor 2. The magnetic disks 28are provided with a dust shield member 6 which prevents dust on themagnetic disks 28 from reaching the distal ends of the magnetic heads 4.

As shown in FIG. 1, a cover 12 constitutes an upper cover of the housing(disk enclosure) which covers the base 11. The cover 12 is made of aferromagnetic material, such as iron plate or Permalloy, to shield anexternal magnetic field. A flexible printed board (circuit board) 15b isprovided on the bottom of the cover 12. This printed circuit board 15bis connected to the printed circuit board 15a of the base 11 by linkportions 15c. Mounted on the printed circuit board 15b is an LSI(circuitry for magnetic recording and reproduction) which will bediscussed later with reference to FIG. 4.

A plurality of shock absorbers 54, which will be described later, areprovided on this printed circuit board 15a in the vicinity of theperiphery of magnetic disks 28. Further, a shield member 50 made of ametal plate, such as a copper plate, having a good conductivity, isprovided on the shock absorbers 54 for providing electric shield. Aferromagnetic member 52 (e.g., iron plate, Permalloy or ferrite) isprovided in association with the location of the magnetic heads 4 toprovide magnetic shield for the magnetic heads 4.

A connector 17 connected to the printed circuit board 15b is furtherprovided on the left end portion of the cover 12. This magnetic diskapparatus is electrically connected to an external computer or the likevia this connector 17.

The magnetic disk apparatus, 3.37 inches (85.6 mm) long, 2.13 inches (54mm) wide and 0.41 inch (10.5 mm) tall, is a micro disk apparatus withthe size of a credit card.

FIGS. 3 and 4 show the cross section of a complete assembly of themagnetic disk apparatus in FIG. 1 with the cover 12 covering the base11. In FIGS. 3 and 4, shafts 13a and 13b respectively constitute thefixed rotary shafts of the spindle motor 2 and the actuator 3. The lowerends of the shafts 13a and 13b are secured to the base 11 by temperaturefitting. The upper ends of the shafts 13a and 13b are securely fastenedto the cover 12 by screws 17.

Mounted on the motor shaft 13a is the spindle motor 2, which supportstwo magnetic disks 28 and rotate at a high speed (e.g., 3600 rpm).Mounted on the actuator shaft 13b is the actuator 4, which holds themagnetic heads 4, and moves and positions each magnetic head 4 to atarget track on the associated magnetic disk 28.

Provided on the inner walls of the base 11 and cover 12 are the flexibleprinted circuit boards 15a and 15b on which LSIs (servo controller, DCmotor controller, read/write controller, interface controller, etc.) 16are mounted. The printed circuit board 15b is connected to the connector17 which is held by the base 11 and the cover 12.

With the connector 17 coupled to the receiving connector of an externaldevice (e.g., a notebook type personal computer), the magnetic diskapparatus serves as a storage device for the external device.

The spindle motor 2 has an in-spindle structure in which the outsidediameter of the DCM (direct current motor) hub or the rotor yoke isnearly equal to the inner diameter of the magnetic disks 28. A stator21, formed by a lamination of silicon steel plates, is provided aroundthe motor shaft 13a. This stator 21 is secured to the shaft 13a by anadhesive. A copper coil 22 is wound around the stator 21. A wire 22a ledfrom this copper coil 22 is soldered to a terminal on the printedcircuit board 15a to supply a drive current to the spindle motor 2.

Reference numeral "23a" denotes a rear bearing, and reference numeral"23b" a top bearing. A spacer 24 serves to keep the gap between the rearbearing 23a and the top bearing 23b. The inner rings of the rear bearing23a and the top bearing 23b are secured to the motor shaft 13a by anadhesive. Reference numeral "25" is a motor hub made of an iron member.The inner periphery of the motor hub 25 is adhered to the outer rings ofthe rear bearing 23a and top bearing 23b.

A magnet 26 is attached to that portion of the motor hub 25 which facesthe stator 21. The stator 21 and the magnet 26 of the motor hub 25constitute a magnetic circuit. When the coil 22 is excited andde-excited alternately, driving power is generated in the magneticcircuit, causing the motor hub 25 to rotate.

Two magnetic disks 28 are sandwiched between a collar 25a of the motorhub 25 and a ring spring 27, with spacer rings 29a and 29b in between.By securing and compressing this ring spring 27 to the motor hub 25 by ascrew 20, compressive force acts between the collar 25a of the motor hub25 and the ring spring 27, thus securing the two magnetic disks 28 tothe spacer rings 29a and 29b.

The actuator 3 will now be described. Referring to FIG. 4, referencenumeral "31a" is a rear bearing and reference numeral "31b" is a topbearing. A spacer 32 keeps the gap between the rear bearing 31a and thetop bearing 31b. The inner rings of the rear bearing 31a and top bearing31b are secured adhered to the actuator shaft 13b. An aluminum block 33has its inner periphery adhered to the outer rings of the rear bearing31a and top bearing 31b. Two collars 33a are provided on one end portionof the block 33, and four arms 34 are secured to the respective sides ofthe collars 33a, one arm to each side of each collar, by an adhesive,for example.

The magnetic heads 4 are securely adhered to the distal ends of therespective arms 34. Each magnetic head 4 faces one surface of theassociated magnetic disk 28. A coil 35 is fixed to the opposite side ofthe block 33 to the collars 33a by resin molding. The magnetic circuit14, constituted by the magnet and iron yoke, is provided on the base 11.The coil 35 is held in the magnetic gap of the magnetic circuit 14.

The coil 35 is connected to a terminal of the printed circuit board 15avia the flat cable 36 provided on the side of the aluminum block 33 ofthe actuator 3. When a current flow through the coil 35, driving poweris generated in the coil 35, causing the actuator 3 to rotate around theactuator shaft 13b. In accordance with a track position signal read bythe magnetic heads 4, the servo controller mounted on the printedcircuit board 15a controls the current flowing through the coil 35 tomove and position each magnetic head 4 to a target track on theassociated magnetic disk 28.

The magnetic heads of the magnetic disk apparatus will now be described.FIG. 5 is an exploded perspective view of the magnetic head assemblyshown in FIG. 1, FIG. 6A is a perspective view of a head chip shown inFIG. 5, FIG. 6B is a cross-sectional view of the head chip in FIG. 5,FIG. 7 is an exploded perspective view of a flexible support shown inFIG. 5, and FIG. 8 is a cross-sectional view of the magnetic headassembly shown in FIG. 5.

As shown in FIG. 5, the magnetic head assembly 4 comprises a head chip4a and a flexible support 4b which supports this head chip 4a. The headchip 4a is formed in a thin-film forming process to have a width W of0.42 mm, a length l of 0.8 mm and a thickness of 0.04 mm, and weights100 mg or less. The head chip 4a will be described later. The flexiblesupport 4b has a width W of 0.42 mm, a length L of 10.7 mm and athickness of 0.05 mm, and will also be described later.

In FIGS. 6A and 6B, the head chip 4a is a probe type vertical magneticrecording head. This head chip 4a comprises a pole (main magnetic pole)43, a yoke 44, a core 45, a return stud 46 and a return yoke 47, all ofwhich constitute a low magnetic resistance path. A high magneticresistance gap is formed between the pole 43 and the return yoke 47. Acontact pad 49 made of a solid member is provided at the pole 43. Aspiral coil 48 is provided around the core 45. A pair of connectorterminals 41 and 42, made of gold (Au), are connected to the coil 45 inan exposed manner. Those connector terminals 41 and 42 are each formedby depositing a thin film in an insulating layer.

As shown in FIG. 6B, the solid contact pad 49 of this head chip 4acontacts the associated two-layer magnetic disk 28 of a verticalmagnetic recording type for data recording/reproduction. The magneticforce from the pole 43 returns, dispersed, between the pole 43 and thereturn yoke 47 from the bottom layer of the magnetic disk 28, so thatonly that portion of the magnetic disk 28 which lies directly under thepole 43 is magnetized, thus accomplishing contact type verticalrecording.

At this time, as the solid contact pad 49 of the head chip 4a contactsthe magnetic disk 28, the head chip 4a has less wear-out even throughcontact recording. This can therefore accomplish stable contactrecording and high-density recording.

The head chip 4a is formed by a lamination of thin films whoselamination direction is vertical to the surface of the magnetic disk 28as indicated by the arrows in FIG. 6B. Since this head chip 4a merelyhas the low magnetic resistance path including the pole 43, the coil 48and the terminals 41 and 42, and has no lead pattern, it can be madeconsiderably small as has been explained with reference to FIG. 5. Thishead chip 4a can therefore be made 1/20 of the size of the one describedin U.S. Pat. No. 5,111,351.

The flexible support 4b for supporting this head chip 4a is formed asfollows. As shown in FIG. 7, an insulating layer 4-2 of an insulatingresin is provided on a flexible metal plate 4-1 of stainless or thelike. Lead patterns and 4-4 of a conductive metal material, such ascopper, are formed on this insulating layer 4-2. Formed on the leadpatterns 4-3 and 4-4 is an insulating protection layer which has holesformed to expose both end portions of each of the lead patterns 4-3 and4-4.

Bump portions 4-6 and 4-7 of gold or the like are provided at theexposed portions of the lead patterns 4-3 and 4-4 at their one end(which are to be connected to the head chip 4a). It is a proximal end4-10 of the flexible support 4b, a large area, which is to be connectedto the associated arm 34 in order to increase the connection strength tothe arm 34 (see FIG. 5 too).

To complete this magnetic head assembly, an insulating adhesive isapplied around the bump portions 4-6 and 4-7 of the flexible support 4bin FIG. 7, and then the terminals and 42 of the head chip 4a arepositioned on the bump portions 4-6 and 4-7 of the flexible support 4bas shown in FIG. 8. Then, the terminals 41 and 42 of the head chip 4aare placed on the bump portions 4-6 and 4-7 and pressure is appliedthereto. As the bump portions 4-6 and 4-7 of the flexible support 4bprotrude, they contact with the terminals 41 and 42 of the head chip 4a,with the other portion of the head chip 4a secured to the flexiblesupport 4b by the adhesive. The provision of the bump portions and 4-7on the flexible support 4b allows the small head chip 4a as wide as 0.5mm to be electrically and securely connected to the flexible support 4b.

Lead wires 37 are connected to the arm-side ends of the lead patterns4-3 and 4-4 of the flexible support 4b, thus completing the magnetichead assembly.

Then, an adhesive is applied to the large proximal end 4-10 of theprotection layer 4-5 of the flexible support and the arm 34 is securelyattached to this proximal end 10. The lead wires 37 are to be connectedto the flat cable 36 mentioned above with reference to FIGS. 1 and 2.

Only the head chip 4a having the low magnetic resistance path includingthe pole, the coil and the terminals is formed on a wafer and the leadpattern portions are formed separately, not on the wafer, whereasconventionally, the lead pattern portions of the flexible magnetic headare formed integrally on the wafer. Accordingly, the number of the headchips 4a to be formed on a single wafer increases to about more than tentimes the number conventionally available. Therefore, the magnetic headassembles can be provided at a low cost, and magnetic disk apparatusesof the vertical magnetic recording type can also be provided at a lowcost.

FIG. 9 is an exploded perspective view of the magnetic disk apparatusshown in FIG. 1, FIG. 10 illustrates how the printed circuit boards ofthe magnetic disk apparatus in FIG. 9 are mounted, FIG. 11 is a top viewof the magnetic disk apparatus, FIG. 12 is a cross-sectional viewshowing the essential portions of the magnetic disk apparatus in FIG. 9,FIG. 13 is a diagram for explaining where shock absorbers of themagnetic disk apparatus are arranged, and FIG. 14 is a diagram forexplaining where a ferromagnetic member of the magnetic disk apparatusin FIG. 9 is arranged.

in FIGS. 9 and 10, the base 11 and the cover 12 are prepared by pressworking of a ferromagnetic body, and the printed circuit boards 15a and15b are connected to each other by the link portions 15c as shown inFIG. 10. As shown in FIG. 10, the printed circuit board 15a provided onthe base 11 has a shape with those portions cut out where the spindlemotor 2, the magnetic circuit 14, the actuator 3 and ferromagneticmembers 52 and 53 (which will be described later) are to be provided.Likewise, the printed circuit board 15b provided on the cover 12 has ashape with those portions cut out where the spindle motor 2, themagnetic circuit 14 and the actuator 3 are to be provided. The printedcircuit boards 15a and 15b are formed integral with the link portions15c connecting both printed circuit boards. Both printed circuit boards15a and 15b are electrically connected together by an electric circuitpatterns of the link portions 15c.

The printed circuit board 15a on the base 11 includes a read/writecontroller (LSI) 16a, a servo controller (LSI) 16b for controlling thespindle motor 2 and the actuator 3, and a data modulator/demodulator(LSI) 16c which performs modulation and demodulation on read data andwrite data, both controllers being of an analog system. The printedcircuit board 15b on the cover 12 includes a microprocessor 16d, aninterface controller 16e, a ROM 16f and a RAM 16g, both controllersbeing of a digital system.

The above circuit arrangements are made because the spindle motor 2, theactuator 3 and the magnetic heads 4, which are controlled by analogsignals, are attached to the base 11. In other words, the analogcontrollers are provided on the printed circuit board 15a on the baseside 11 to shorten the signal paths for analog signals.

The shook absorbers 54 for absorbing a shock on the magnetic disks 28,which originate from the vibration of the magnetic disks 28 caused by anexternal shock applied thereto, are provided on the printed circuitboards 15a and 15b. The shock absorbers 54 are formed of an elasticmember having viscosity. For example, fluorocarbon rubber, butyl rubberand the like are preferable while silicone rubber having no viscosity isnot preferable.

The shock absorbers 54 are provided on those portions of the printedcircuit boards 15a and 15b where the LSIs 16 and wiring patterns are notlocated. For instance, three shock absorbers 54a, 54b and 54c areprovided on the printed circuit board 15a around the spindle motor asshown in FIG. 11, while six shock absorbers 54d, 54e, 54f, 54g and 54hare provided on the printed circuit board 15b around the spindle motorportion.

The shock absorbers 54 should be designed taller than the maximum heightof the LSIs 16 mounted on the printed circuit boards 15a and 15b. Inthis example, the shock absorbers 54 are made taller than the LSIs 16 by0.25 mm, as shown in FIG. 12.

The connector 17 is connected to one end portion of the printed circuitboard 15b. The thus formed integral body of the printed circuit boards15a, 15b and 15c is attached to the base 11 and the cover 12 as shown inFIG. 10. That is, the printed circuit board 15a is attached to thebottom of the base 11 and the printed circuit board 15b to the bottom ofthe cover 12 by an adhesive or the like. Then, the ferromagnetic members52 and 537 are provided in those of the base 11 and cover 12 where themagnetic heads 4 are movable. The reason for the provision of theferromagnetic members 52 and 53 will be given later.

The shield members 50 and 51 are provided on the printed circuit boards15a and 15b or the shock absorbers 54. The shield members 50 and 51 areformed of a metal plate of copper or the like which has a goodconductivity, and are about 0.2 mm thick. Those shield members 50 and 51serve to shield the magnetic heads 4 from electric noise generated fromthe LSIs 16 and the wiring patterns. In this respect, the shield members50 and 51 are shaped to cover the LSIs 16, which may cause noise, asshown in FIGS. 9 and 11.

As shown in FIG. 11, the actuator 3 on which the magnetic heads 4 aremounted is attached to the thus formed base 11. Then, the spindle motor2 on which the magnetic disks 28 are mounted are attached to the base11. Then, the magnetic circuit 14 is attached, followed by theattachment of the dust shield member 6. The flat cable 36 of theactuator 4 is securely and electrically connected to the printed circuitboard 15a, thus permitting the actuator 3 and spindle motor 2 to beelectrically connected to the printed circuit board 15a.

Folding the resultant structure at the link portions 15c of the printedcircuit board assembly, the cover 12 is placed over the base 11 and issecured to the base 11 by screws or the like, thus completing themagnetic disk apparatus.

The thus constituted magnetic disk apparatus has the printed circuitboards 15a and 15b attached to the inner wall of the ferromagnetichousing (base 11 and cover 12) as slim as about 0.5 mm as shown in FIG.12. The controller LSIs 16 are mounted on the printed circuit boards 15aand 15b. The height of the printed circuit boards plus the height of theLSIs is about 1.75 mm.

The shock absorbers 54a to 54h provided on the printed circuit board 15aand 15b have a height of about 2.0 mm from the inner wall of thehousing, about 0.25 mm taller than the LSIs. The electric shield members50 and 51 about 0.2 mm thick are provided on the shock absorbers54a-54h. The distance from the electric shield members 50 and 51 to themagnetic disks 28 is about 0.3 mm.

The function of the shock absorbers 54 will now be described. Theaforementioned detachable type magnetic disk apparatus may be dropped ona floor or the like by accident. In this case, the magnetic diskapparatus would receive an external shock of more than 300 G. Thedistance between the magnetic disks 28 and the housing is just about 2.0mm. Without the shock absorbers 54, therefore, when an external shock ofsuch a magnitude is applied to the magnetic disk apparatus, the magneticdisks 28 vibrate so that the displacement of the magnetic disks 28 attheir outermost peripheral portions become large. As a result, themagnetic disks 28 are likely to hit against the housing and may bedamaged.

If the circuitry portions, such as the LSIs, are providing in thehousing, the distance between the magnetic disks 28 and the circuitryportions becomes smaller, thus increasing the possibility of damagingthe magnetic disks 28. Further, the internal circuits may also bedamaged.

As a solution to this problem, the shock absorbers 54 are provided inthe housing to suppress the vibration of the magnetic disks 28 andprevent the magnetic disks 28 from hitting against the housing. At thistime, the shock absorbers 54 need viscosity in addition to elasticity astheir characteristics. If the shock absorbers 54 merely have elasticity,repulsive force would be generated, preventing the shock absorbers 54from absorbing the vibration of the magnetic disks 28. With theviscosity also given, the shock absorbers 54 can absorb the force of thevibration of the magnetic disks 28 and can thus suppress thedisplacement of the magnetic disks 28.

In this case, if the circuits are provided in the housing, the shockabsorbers 54 should be designed taller than the circuitry portions. Thisis because that if the magnetic disks 28 come in contact with thecircuitry portions before contacting the shock absorbers 54 due to someapplied external shock, the magnetic disks 28 may collide hard with thecircuitry portions and would be damaged, in which case the provision ofthe shock absorbers 54 would become insignificant.

As the displacement of each magnetic disk 28 becomes largest at itsoutermost peripheral portion, it is desirable to provide the shockabsorbers 54 in the vicinity of the outermost peripheral portion of themagnetic disks 28, as shown in FIG. 13.

In consideration of an external shock applied from all the directions,it is desirable to provide the shock absorbers 54 at three or morepositions of different directions around the spindle motor 2 withrespect to the magnetic disks 28, as shown in FIG. 13. In this respect,the three shock absorbers 54a, 54b and 54c are provided at threepositions of different directions on the base side 11 in the exampleshown in FIGS. 10 and 11. The three shock absorbers 54d, 54e and 54h areprovided at three directionally different positions around the spindlemotor 2 on the cover side 12. The shock absorbers 54f and 54g areadditionally provided to support the electric shield member 50 at itsend portion as well as to absorb a shock.

The housing (base 11 and cover 12) is made of a ferromagnetic materialto protect the recording magnetization of the magnetic disks 28 and therecording/reproducing actions of the magnetic heads 4 from theaforementioned external magnetic field. The external magnetic fieldmagnetizes the head portion of each magnetic head 4, causing a dataerror at the time of data recording/reproduction. Basically, therefore,the ferromagnetic member 53 for shielding an external magnetic field isprovided in the movable range of the magnetic heads 4, as shown in FIG.14.

In the vertical recording system, the direction of magnetization of themagnetic disks 28 is in the thickness direction of the magnetic disks28. Further, the magnetic disk apparatus is slim in the thicknessdirection of the magnetic disks 28, so that the direction ofmagnetization of the magnetic disks 28 may be changed by an externalmagnetic field. It is therefore necessary to magnetically shield themagnetic disks 28 too, so that the housing itself is made of aferromagnetic material. As this ferromagnetic material is heavier thanaluminum, increasing the thickness of the housing to improve theshielding effect increases the weight of the magnetic disk apparatusitself and is not desirable. Accordingly, the housing made of aferromagnetic material is made just thick enough (e.g., about 0.5 mm) toeliminate the influence of the external magnetic field on the magneticdisks 28 and the ferromagnetic members 52 and 53 are further provided tothose portions of the magnetic heads 4 which are likely to be affectedby the external magnetic field. This way, a sufficient magnetic fieldshielding effect can be provided without making the magnetic diskapparatus unnecessarily heavier.

The electric shield members 50 and 51 are provided on the LSIs 16 of theprinted circuit boards 15a and 15b for the following reason. Electricnoise may be generated from the terminals of the LSIs 16 and the wiringpatterns of the printed circuit boards 15a and 15b. This noise mayaffect the recording/reproducing function of the magnetic heads 4,causing a data error. Particularly, as the signal frequency becomeshigher with the recent improvement on the recording density, noise islikely to occur.

In this respect, the electric shield members 50 and 51 are provided onthe LSIs 16 of the printed circuit boards 15a and 15b to shield themagnetic heads 4 from possible electric noise generated from the LSIs16, etc.

In this case, the aforementioned external shock on the magnetic disks 28will be absorbed by the shock absorbers 54 through the electric shieldmembers 50 and 51. In other words, the magnetic disks 28 would hitagainst the shield members 50 and 51 of metal, and may be damaged by themetal-to-metal collision. In this respect, layers of resin, such aspolyimide, are provided on those sides of the copper shield members 50and 51 where the magnetic disks 28 are located. The direct collision ofthe magnetic disks 28 with the shield members 50 and 51 is prevented toprevent scratches from being made on the magnetic disks 28, using theelasticity of the polyimide resin layer.

It is better if such polyimide resin layers are also provided on thosesides of the shield members 50 and 51 where the printed circuit boards15a and 15b are located. This is because that the electric shieldmembers 50 and 51 may directly contact the printed circuit boards 15aand 15b at the portions where the shock absorbers 54 or the LSIs 16 arenot provided. The insulating polyimide resin layer, if provided on theprinted circuit board sides of the shield members 50 and 51, can preventthe contact of the shield members 50 and 51 with the printed circuitboards 15a and 15b from affecting the circuitry. In addition, as thoseresin layers cover the electric shield members 50 and 51 made of copper,they also serve to prevent rustable copper from being rusted.

The provision of the shock absorbers in the housing in theabove-described manner can suppress the external-shock originateddisplacement of the magnetic disks 28, thus preventing the magneticdisks 28 from being damaged by the external shock. If the housing (base11 and cover 12) is made of a ferromagnetic material, the magnetic disks28 and the magnetic heads 4 can be protected from an external magneticfield. At this time, the increase in the weight of the magnetic diskapparatus can be minimized by minimizing the thickness of theferromagnetic material for the housing and providing additionalferromagnetic members 52 and 53 to the magnetic heads 4 which will beaffected most by the external magnetic field.

Further, as the controllers-mounted printed circuit boards are placed inthe housing, the magnetic disk apparatus including the printed circuitboards can be made shorter. Although the printed circuit boards areplaced in the housing, the provision of the electric shield members 50and 51 can protect the magnetic heads 4 from electric noise generatedfrom the printed circuit boards.

Furthermore, the shock absorbers 54 are made of a material having bothviscosity and elasticity, the vibration of the magnetic disks 28 can bereduced by the elasticity as well as can be absorbed by the viscosity.As the shock absorbers 54 are provided in the vicinity of the outermostperipheral portion of the magnetic disks 28 where the vibrationdisplacement is the largest, the vibration of the magnetic disks 28 canbe suppressed while it is still small. In addition, as the shockabsorbers 54 are provided at a plurality of positions near the outermostperipheral portion of the magnetic disks 28, the vibration of themagnetic disks 28 in any circumferential direction can be suppressed.

Modifications of this invention will now be described. FIG. 15 is across-sectional view showing the essential portions of a modification ofthe magnetic disk apparatus of this invention. FIG. 15 presents a crosssection of the magnetic disk apparatus at the same position as in FIG.12.

This modification has the structure of the embodiment shown in FIG. 12plus an electric-wave shield layer 55a provided between the base 11 andthe printed circuit board 15a and an electric-wave shield layer 55bprovided between the cover 12 and the printed circuit board 15b as shownin FIG. 15.

When a computer or the like incorporated a magnetic disk apparatus isplaced near a television set or the like which has strong leak waves,the LSIs 16 on the printed circuit boards 15a and 15b in the magneticdisk apparatus may malfunction or the read/write performance of themagnetic heads 4 may be reduced due to the leak noise, causing a dataerror.

The penetration of the external electric wave noise into thenoise-susceptive components can be prevented by the electric-wave shieldlayers 55a and 55b. A preferable material for the electric-wave shieldlayers 55a and 55b is metal having good conductivity, such as copper. Ifinsulating layers are provided at least on those surfaces of theelectric-wave shield layers 55a and 55b of metal such as copper wherethe printed circuit boards 15a and 15b are located, the pins of the LSIsmounted on the printed circuit boards 15a and 15b will not beshort-circuited. Such an insulating layer may also be provided on thebase side (11) or the cover side (12) of each of the electric-waveshield layers 55a and 55b to prevent the material for thoseelectric-wave shield layers, copper, from being easily rusted.

If electric-wave shield layers like copper-plated layers are provided onthe magnetic head sides (4) of the ferromagnetic members 52 and 53provided in the movable range of the magnetic heads 4, which have beendescribed referring to FIGS. 9 and 14, the magnetic heads 4 can also beprotected from an external electric wave noise.

FIG. 16 is a cross-sectional view showing the essential portions ofanother modification of the magnetic disk apparatus of this invention.According to this modification, the base 11 and cover 12 in the magneticdisk apparatus of the embodiment shown in FIG. 12 are made ofnon-magnetic metal, such as aluminum. The use of aluminum for thehousing constituted of the base 11 and cover 12 contributes tofacilitating the manufacturing of the base 11 and the cover 12 due toits easy processing as well as making the magnetic disk apparatuslighter.

In this modification, a ferromagnetic member 56a of iron, Permalloy orthe like, about 0.25 mm thick, is arranged on the base 11, with theprinted circuit board 15a provided on the member 56a. Likewise, anotherferromagnetic member 56b of iron, Permalloy or the like, about 0.25 mmthick, is arranged on the cover 12, with the printed circuit board 15bprovided on the member 56b. Like the embodiment shown in FIG. 12, thismodification can provide magnetic shield against an external magneticfield. In this example, the shock absorbers 54 are also provided on theprinted circuit boards 15a and 15b to improve the shock resistance.

Further, if electric-wave shield layers like copper-plated layers areprovided on the ferromagnetic members 56a and 56b, an external electricwave can be shielded.

If the ferromagnetic members 56 are provided in the movable range of themagnetic heads 4, it is possible to magnetically shield the magneticheads 4. In this case, it is better if the ferromagnetic members 56provided in the movable range of the magnetic heads 4 be made thickerthan the ferromagnetic members 56a and 56b provided under the printedcircuit boards.

FIG. 17 is a cross-sectional view showing the essential portions of afurther modification of the magnetic disk apparatus of this invention.This modification has the structure of the modification in FIG. 16 pluselectric shield members 50 and 51 provided on the LSIs 16 on the printedcircuit boards 15a and 15b, thus shielding the magnetic heads 4 fromelectric noise generated from the LSIs 16.

In this case, like in the example of FIG. 16, layers of resin, such aspolyimide resin layers 57, are provided on the magnetic disk sides ofthe copper shield members 50 and 51 to cope with an external shock. Thedirect collision of the magnetic disks 28 with the shield members 50 and51 is prevented to prevent scratches from being made on the magneticdisks 28, using the elasticity of the polyimide resin layer.

It is better if polyimide resin layers 58 are also provided on thosesides of the shield members 50 and 51 where the printed circuit boards15a and 15b are located. This is because that the electric shieldmembers 50 and 51 may directly contact the printed circuit boards 15aand 15b at the portions where the shock absorbers 54 or the LSIs 16 arenot provided. The insulating polyimide resin layer, if provided on theprinted circuit board sides of the shield members 50 and 51, can preventthe contact of the shield members 50 and 51 with the printed circuitboards 15a and 15b from affecting the circuitry. In addition, as thoseresin layers cover the electric shield members 50 and 51 made of copper,they also serve to prevent rustable copper from being rusted.

In this example, the shock absorbers 54 are also provided on the printedcircuit boards 15a and 15b to improve the shook resistance.

FIG. 18A is a structural diagram of a still another modification of themagnetic disk apparatus of this invention, showing the outline of themagnetic disk apparatus. In this modification, instead of providing theshock absorbers 54 in the housing 11, 12 as in the embodiment shown inFIG. 12, shock absorbers 54-1 are provided on the outer surfaces of thehousing 11, 12. As shown in the cross-sectional view of FIG. 18B, arecess 11-1 is provided in the side surface of the base 11 and one shockabsorber 54-1 is placed there. Likewise, a recess 12-1 is provided inthe side surface of the cover 12 and another shock absorber 54-1 isplaced there. It is desirable that the shock absorbers 54-1 be made of aviscous and elastic material as in the embodiment in FIG. 12; one of theproper materials is fluorocarbon rubber.

With the above structure, when the magnetic disk apparatus is dropped ona floor or the like, a shock applied in entirety to the sides of themagnetic disk apparatus can be reduced. It is therefore possible tosuppress the displacement of the magnetic disks due to a shock appliedfrom the sides of the apparatus, thus preventing the magnetic disks 28and magnetic heads 4 from being damaged.

FIG. 19A is a structural diagram of a still further modification of themagnetic disk apparatus of this invention, showing the exterior of theapparatus. This modification is the modification shown in FIGS. 18A and18B, with the shock absorbers 54-1 provided on both the upper and lowerend portions of the base 11 and cover 12 as shown in the cross-sectionalview of FIG. 19B. More specifically, a recess 11-1 is provided in theside surface of the base 11 and one shock absorber 54-1 is providedbetween both end portions of the base 11. Likewise, a recess 12-1 isprovided in the side surface of the cover 12 and another shock absorber54-1 is placed between both end portions of the cover 12. It isdesirable that the shock absorbers 54-1 be made of a viscous and elasticmaterial as in the embodiment in FIG. 12; one of the proper materials isfluorocarbon rubber.

With the above structure, when the magnetic disk apparatus is dropped ona floor or the like, a shock applied in entirety to the sides of themagnetic disk apparatus can be reduced. It is therefore possible tosuppress the displacement of the magnetic disks due to a shock appliedfrom the sides of the apparatus, thus preventing the magnetic disks 28and magnetic heads 4 from being damaged. It is also possible to preventthe spindle motor or the like from being damaged by a shock applied fromthe top and bottom directions in the diagram.

As the shock absorbers 54-1 are provided in the recesses 11-1 and 12-1formed in the sides of the housing 11, 12, the magnetic disk apparatusneed not be made tall so much even through the shock absorbers 54 areactually provided on the outer surfaces of the housing 11, 12.

FIG. 20 is a perspective view for explaining a yet still furthermodification of the magnetic disk apparatus of this invention, and FIG.21 is a cross-sectional view of the magnetic disk apparatus in FIG. 20.With the use of a contact recording system in which the magnetic heads 4contact the magnetic disks 28, as described earlier, wear-out powder isproduced between the magnetic head 4 and the associated magnetic disk28. As that magnetic disk 28 rotates, this wear-out powder returns tothe magnetic head 4 and comes between that magnetic head 4 and theassociated magnetic disk 28. This reduces the recording/reproducingcharacteristics of the magnetic heads 4, causing a data error.

It is therefore necessary to remove dust, such as wear-out powder, fromthe surfaces of the magnetic disks 28. In this respect, a dust shieldmember 6 is provided for the surface of each magnetic disk 28. The dustshield members 6 are provided as follows. As shown in FIG. 21, attachingportions 60-1 and 60-3 provided respectively on the cover 12 and thebase 11, with another attaching portion 60-2 provided between themagnetic disks 28. The dust shield members 61 are provided on thoseattaching portions 60-1 to 60-3. It is desirable that the dust shieldmembers 61 are of a soft material, such as dust-free paper or dust-freecloth; for example, "Kim-wipe," a product name, is a proper material.

This dust shield member 61 needs to partially or entirely contact thesurface of the associated magnetic disk 28, thereby cleaning dust offthat disk surface so that dust, such as wear-out powder will not remainon the disk surface.

Each dust shield member 61 is tilted at a given angle to the surface ofthe associated magnetic disk 28, as shown in FIGS. 20 and 21, so that itwill not become any rotational load on the magnetic disk 28. Further,the dust shield member 61 is located at the back of the associatedmagnetic head 4 in the rotational direction of the magnetic disk 28 sothat wear-out powder produced by that magnetic head 4 is wiped outimmediately after the magnetic head 4.

In addition to the above-described embodiments and modifications, thepresent invention can be worked in various other modifications. First,although the foregoing description has been given with reference to thecontact type magnetic heads, this invention may be applied to float typemagnetic heads as well. Secondly, although the controllers-mountedprinted circuit boards have been explained to be installed in themagnetic disk apparatus, the shook absorbers 54 may be provided directlyon the base 11 and the cover 12 if no controllers are to be installedinside the apparatus. Thirdly, if there is no need to shield an externalmagnetic field, the base 11 and the cover 12 may be made of anon-magnetic material and no ferromagnetic layers need to be provided.Fourthly, although the foregoing description has been given of the casewhere two magnetic disks are provided in the magnetic disk apparatus,the apparatus may comprise one magnetic disk or three or more magneticdisks. Fifthly, although the foregoing description has been given of thecase of the vertical recording, this invention can also be applied to ahorizontal magnetic recording system in which case the ferromagneticmembers for shielding a magnetic field have only to be disposed in themovable range of the magnetic heads 4.

In short, according to this invention, an external magnetic field can beshielded without changing the size of the apparatus. An externalelectric wave noise as well as an internal electric wave noise can alsobe shielded without changing the size of the apparatus. Further, it ispossible to prevent the magnetic recording/reproducing characteristicfrom being impaired by dust generated by the contact type magneticrecording.

What is claimed is:
 1. A magnetic disk apparatus comprising:at least onemagnetic disk; rotation means for rotating the magnetic disk; a magnetichead for recording and reproducing information on and from the magneticdisk; an actuator for supporting the magnetic head and moving themagnetic head to a given position on the magnetic disk; an enclosure,made of a ferromagnetic material, for covering said disk, rotationmeans, head and actuator; a shield layer made of a ferromagneticmaterial and provided inside the enclosure in that region of theenclosure which corresponds to a movable range of the magnetic head; aconductive metal layer provided on the shield layer; a circuit boardprovided on an inner wall of the enclosure, said circuit board havingcircuitry mounted on the circuit board for accomplishing magneticrecording and reproduction; and a conductive shield member providedbetween the magnetic disk and circuit board.
 2. A magnetic diskapparatus comprising:at least one magnetic disk; rotation means forrotating the magnetic disk; a magnetic head for recording andreproducing information on and from the magnetic disk; an actuator forsupporting the magnetic head and moving the magnetic head to a givenposition on the magnetic disk; an enclosure, made of a ferromagneticmaterial, for covering said disk, rotation means, head and actuator; acircuit board provided on an inner wall of the enclosure, said circuitboard having circuitry mounted on the circuit board for accomplishingmagnetic recording and reproduction; a shield layer provided between theenclosure and the circuit board for shielding external noise and havingan insulating layer at least on the surface of the shield layer wherethe circuit board is located; and a conductive shield member providedbetween the magnetic disk and the circuit board.
 3. The magnetic diskapparatus according to claim 2, wherein the shield layer is made ofcopper.
 4. The magnetic disk apparatus according to claim 2, wherein theconductive shield member is mounted on part of the circuit board.
 5. Themagnetic disk apparatus according to claim 2, further comprising a shockabsorber, provided between the magnetic disk and the circuit board forabsorbing vibration of the magnetic disk, said shock absorber beingprovided between the circuit board and the magnetic disk and carryingsaid conductive shield member thereon.
 6. The magnetic disk apparatusaccording to claim 2, further comprising a dust shield member locatedimmediately behind the magnetic head in the rotational direction of themagnetic disk for removing and holding dust produced on a surface of themagnetic disk which the magnetic head contacts for recording andreproduction.
 7. A magnetic disk apparatus comprising: at least onemagnetic disk;rotation means for rotating the magnetic disk; a magnetichead for recording and reproducing information on and from the magneticdisk; an actuator for supporting the magnetic head and moving themagnetic head to a given position on the magnetic disk; an enclosure,made of a ferromagnetic material, for covering said disk, rotationmeans, head and actuator; a circuit board provided on an inner wall ofthe enclosure, said circuit board having circuitry mounted on thecircuit board for accomplishing magnetic recording and reproduction; aconductive shield member provided between the magnetic disk and thecircuit board; and a shock absorber, provided between the circuit boardand the magnetic disk, for supporting the shield member and absorbingvibration of the magnetic disk, said shield member being connected to asurface of said shock absorber, said surface being disposed between themagnetic disk and the circuit board.
 8. A magnetic disk apparatuscomprising:at least one magnetic disk; rotation means for rotating themagnetic disk; a magnetic head for recording and reproducing informationon and from the magnetic disk; an actuator for supporting the magnetichead and moving the magnetic head to a given position on the magneticdisk; an enclosure, made of a ferromagnetic material, for covering saiddisk, rotation means, head and actuator; a circuit board provided on aninner wall of the enclosure; and a shock absorber, provided between themagnetic disk and the circuit board for absorbing vibration of themagnetic disk.
 9. A magnetic disk apparatus comprising:at least onemagnetic disk; rotation means for rotating the magnetic disk; a magnetichead for recording and reproducing information on and from the magneticdisk; an actuator for supporting the magnetic head and moving themagnetic head to a given position on the magnetic disk; an enclosure,made of a ferromagnetic material, for covering said disk, rotationmeans, head and actuator; a shield layer made of a ferromagneticmaterial and provided inside the enclosure in that region of theenclosure which corresponds to a movable range of the magnetic head; acircuit board provided on an inner wall of the enclosure, said circuitboard having circuitry for accomplishing magnetic recording andreproduction being mounted of the circuit board; a second shield layerprovided between the enclosure and the circuit board; and a conductiveshield member provided between the magnetic disk and circuit board. 10.A magnetic disk apparatus comprising:at least one magnetic disk;rotation means for rotating the magnetic disk; a magnetic head forrecording and reproducing information on and from the magnetic disk anactuator for supporting the magnetic head and moving the magnetic headto a given position on the magnetic disk an enclosure, made of aferromagnetic material for covering said disk rotation mean, head andactuator; a shield layer made of a ferromagnetic material and providedinside the enclosure in that region of the enclosure-which correspondsto a movable range of the magnetic head; a circuit board provided on aninner wall of the enclosure, circuitry for accomplishing magneticrecording and reproduction being mounted on the circuit board; and aconductive shield member provided between the magnetic disk and thecircuit board.
 11. The magnetic disk apparatus according to claim 10,wherein the conductive shield member is-mounted on part of the circuitboard.
 12. The magnetic disk apparatus according to claim 10, furthercomprising a shock absorber, provided between the magnetic disk and thecircuit board for absorbing vibration of the magnetic disk.
 13. Amagnetic disk apparatus comprising:at least one magnetic disk; rotationmeans for rotating the magnetic disk; a magnetic head for recording andreproducing information on and from the magnetic disk; an actuator forsupporting the magnetic head and moving the magnetic head to a givenposition on the magnetic disk; an enclosure, made of a non-magneticmaterial, for coveting said disk rotation means, head and actuator; ashield layer made of a ferromagnetic material and provided at least inthat region of an inner wall of the enclosure which corresponds to amovable range of the magnetic head; a circuit board provided on an innerwall of the enclosure, said circuit board having circuitry mounted onthe circuit board for accomplishing magnetic recording and reproduction;a second shield layer provided between the enclosure and the circuitboard for shielding external noise and having an insulating layer atleast on the surface of the second shield layer where the circuit boardis located; and a conductive shield member provided between the magneticdisk and the circuit board.
 14. The magnetic disk apparatus according toclaim 13, wherein the second shield layer is made of copper.
 15. Themagnetic disk apparatus according to claim 13, further comprising ashock absorber, provided on the circuit board, for supporting theconductive shield member and absorbing vibration of the magnetic disk,said shock absorber being provided between the circuit board and themagnetic disk and carrying said conductive shield member thereon.
 16. Amagnetic disk apparatus comprising:at least one magnetic disk; rotationmeans for rotating the magnetic disk; a magnetic head for recording andreproducing information on and from the magnetic disk; an actuator forsupporting the magnetic head and moving the magnetic head to a givenposition on the magnetic disk; an enclosure, made of a non-magneticmaterial, for covering said disk, rotation means, head and actuator; ashield layer made of a ferromagnetic material and provided at least inthat region of an inner wall of the enclosure which corresponds to amovable range of the magnetic head; a circuit board provided on an innerwall of the enclosure, said circuit board having circuitry mounted onthe circuit board for accomplishing magnetic recording and reproduction;a conductive shield member provided between the magnetic disk and thecircuit board; and a shock absorber, provided between the circuit boardand the magnetic disk for supporting the conductive shield member andabsorbing vibration of the magnetic disk, said conductive shield memberbeing connected to a surface of said shock absorber, said surface beingdisposed between the magnetic disk and the circuit board.
 17. A magneticdisk apparatus comprising:at least one magnetic disk; rotation means forrotating the magnetic disk; a magnetic head for recording andreproducing information on and from the magnetic disk; an actuator forsupporting the magnetic head and moving the magnetic head to a givenposition on the magnetic disk; an enclosure, made of a non-magneticmaterial, for covering said disk rotation means, head and actuator; ashield layer made of a ferromagnetic material and provided at least inthat region of an inner wall of the enclosure which corresponds to amovable range of the magnetic head; a circuit board provided on an innerwall of the enclosure; and a shock absorber, provided between themagnetic disk and the circuit board for absorbing vibration of themagnetic disk.
 18. A magnetic disk apparatus comprising;at least onemagnetic disk; rotation means for rotating the magnetic disk; a magnetichead for recording and reproducing information on and from the magneticdisk; an actuator for supporting the magnetic head and moving themagnetic head to a given position on the magnetic disk; an enclosure forcovering said disk, rotation means, head and actuator; a circuit boardprovided on an inner wall of the enclosure, said circuit board havingcircuitry mounted on the circuit board for accomplishing magneticrecording and reproduction; a shield layer provided between theenclosure and the circuit board for shielding external noise and havingan insulating layer at least on the surface of the shield layer wherethe circuit board is located; and a conductive shield member providedbetween the magnetic disk and the circuit board.
 19. The magnetic diskapparatus according to claim 18, wherein the shield layer is made ofcopper.
 20. A magnetic disk apparatus comprising:at least one magneticdisk; rotation means for rotating the magnetic disk; a magnetic head forrecording and reproducing information on and from the magnetic disk; anactuator for supporting the magnetic head and moving the magnetic headto a given position on the magnetic disk; an enclosure for covering saiddisk, rotation means, head and actuator; a circuit board provided on aninner wall of the enclosure, said circuit board having circuitry mountedon the circuit board for accomplishing magnetic recording andreproduction; a conductive shield member provided between the magneticdisk and the circuit board; and a shock absorber, provided on thecircuit board, for supporting the shield member and absorbing vibrationof the magnetic disk.